The popularity of autologous blood salvage continues to increase as its many advantages are recognized. Relative to the use of donor blood transfusions, the collection of a patient's blood during an intraoperative procedure and subsequent re-infusion of separated red blood cells (RBCs) into the patient reduces concerns relating to the possibility of disease transmission. The procedure also reduces concerns regarding fibrile/allergic reactions. Further, autologous blood recovery procedures provide ready RBC availability, reduced compatibility test needs, and improved RBC quality advantages.
In known autologous blood salvage techniques, blood is removed from or about a surgical site via a hand-held suction device, mixed with an anticoagulant, and transferred to a reservoir for subsequent transfer and batch processing. In connection with such collection/transfer, the blood is typically filtered to remove debris and defoamed to remove gaseous components. During processing, the blood and a wash solution are separately pumped in sequence through a rotating centrifuge to separate and wash accumulated red blood cells. Following one or more blood fill/RBC separation and wash cycles, the accumulated red blood cells are removed from the centrifuge bowl for subsequent re-infusion to the patient.
During the iterative fill/wash cycles it is important to closely control/monitor the speed and level of RBC collection in order to obtain a high quality RBC product as rapidly/efficiently as possible (e.g. to obtain a high hematocrit and high quality wash, with minimal RBC spillover in the wash solution). In this regard, the reduction of blood processing time is advantageous since, inter alia, it desirably reduces medical personnel time demands and otherwise advantageously allows for expeditious reinfusion of the RBC product to the patient.
With the increase in popularity of blood salvage techniques, heightened performance objectives are being considered. In particular, the enhanced washing of RBCs during rapid processing is of specific interest. As will be appreciated, washing of the red blood cells serves to dilute and remove soluble molecules suspended in the plasma, such as plasma-free hemoglobin and anticoagulants heparin). Additionally, activated/nonactivated clotting factors are removed. Further, it is desirable that washing remove activated platelets/white blood cells. Correspondingly, it is desirable to avoid the accumulation of deposits of white blood cells and platelets in the centrifuge bowl during processing so as to reduce any risk of removal of such deposits with the harvested RBCs. (See e.g., Bull et al., "Enhancing the Safety of Intraoperative RBC Salvage", The Journal of Trauma (March 1989)).